The present invention relates to a combined surgical needle-suture device and, more particularly, to such a device in which a shrinkable tubing attaches a suture to a surgical needle.
For many years, surgeons have employed needle-suture combinations in which the tip of the suture or ligature is attached to the blunt, or shank, end of the needle. Such needle-suture combinations are provided for a wide variety of monofilament and braided suture materials, e.g., nonabsorbable materials such as surgical gut, silk, nylon, polyester, polypropylene, linen and cotton, and absorbable materials such as the synthetic polymers and copolymers of glycolic and lactic acids.
Needle-suture combinations fall into two general classes: standard needle-suture devices and standard detachable needle-suture devices. In the case of standard needle-suture devices, the suture is securely attached to the needle and is not intended to be separable therefrom except by a deliberate cutting or severing of the suture. By contrast, in standard detachable needle-suture devices, separation of the needle from the suture is achieved by application of a separation, or pull-out, force applied by the surgeon. Minimum acceptable pull-out forces required to separate a needle from a suture (for various suture sizes) are set forth in the United States Pharmacopeia (USP). The United States Pharmacopeia prescribes minimum individual pull-out forces and minimum average pull-out forces as measured for five needle-suture combinations. The minimum pull-out forces for both standard and removable needle-suture attachment set forth in the USP are hereby incorporated by reference and are as follows.
______________________________________ Standard Needle Attachment for Absorbable And Nonabsorbable Sutures Metric Size Limits on Needle (Gauge No.) Attachment Nonabsorbable Indi- Absorbable and Synthetic Average vidual (Collagen) Absorbable UPS (kgf) (kgf) Suture Suture Size (Min.) (Min.) ______________________________________ 0.1 11-0 0.007 0.005 0.2 10-0 0.014 0.010 0.4 0.3 9-0 0.021 0.015 0.5 0.4 8-0 0.050 0.025 0.7 0.5 7-0 0.080 0.040 1 0.7 6-0 0.17 0.08 1.5 1 5-0 0.23 0.11 2 1.5 4-0 0.45 0.23 3 2 3-0 0.68 0.34 3.5 3 2-0 1.10 0.45 4 3.5 0 1.50 0.45 5 4 1 1.80 0.60 6 & larger 5 & larger 2 & larger 1.80 0.70 ______________________________________ The requirements are met if neither the average of 5 values nor any individual value is less than the limit given in the foregoing table.
______________________________________ Removable Needle Attachment for Absorbable and Nonabsorbable Sutures Metric Size (Gauge No.) Nonabsorbable Attachment Limits Absorbable and Synthetic USP Minimum Maximum (Collagen) Absorbable Size (kgf) (kgf) ______________________________________ 1.5 1 5-0 2 1.5 4-0 3 2 3-0 3.5 3 2-0 0.028 1.59 4 3.5 0 5 4 1 6 5 2 ______________________________________
One typical method for securing a suture to a needle involves providing a cylindrical recess in the shank end of a needle and securing a suture therein. For example, U.S. Pat. No. 1,558,037 teaches the addition of a cement material to such a substantially cylindrical recess to secure the suture therein. Additional methods for bonding a suture within a needle bore are described in U.S. Pat. Nos. 2,928,395 (adhesives) and 3,394,704 (bonding agents). Alternatively, a suture may be secured within an axial bore in a needle by swaging the needle in the region of the recess. See, e.g., U.S. Pat. No. 1,250,114. Additional prior art methods for securing a suture within a needle bore include expansion of a catgut suture through the application of heat (U.S. Pat. No. 1,665,216), inclusion of protruding teeth within the axial bore to grasp an inserted suture (U.S. Pat. No. 1,678,361) and knotting the end of the suture to be inserted within the bore to secure the suture therein (U.S. Pat. No. 1,757,129).
Methods for detachably securing a suture to a needle are also well known. For example, U.S. Pat. Nos. 3,890,975 and 3,980,177 teach swaging a suture within a needle bore such that the suture has a pull-out valve of 3 to 26 ounces. Alternative detachable attachment methods include providing a weakened suture segment (U.S. Pat. No. 3,949,756), lubricant tipping the end of a suture to be inserted in the axial bore of a needle (U.S. Pat. No. 3,963,031) and pre-tensioning a suture that is swaged within an axial needle bore (U.S. Pat. No. 3,875,946). See also, U.S. Pat. Nos. 3,799,169; 3,880,167; 3,924,630; 3,926,194; 3,943,933; 3,981,307; 4,124,027; and, 4,127,133.
Another method for attaching a suture to a needle involves the use of tubing which is secured to the shank end of the needle and to the suture. For example, U.S. Pat. No. 1,613,206 describes the use of a tubing (preferably silver) which is secured to the shank end of a needle and to a ligature. It is suggested that the tube may be attached to the needle by pressure or soldering and to the ligature by pressure or cementing. It is also suggested that the shank of the needle be of reduced cross section and that the furthest extremity of the reduced diameter shank section be provided with a spike or point upon which the suture may be secured prior to tube application.
U.S. Pat. No. 2,240,330 describes a tubing attachment method whereby the tubing and suture are releasably secured to the needle. In particular, the needle and tubing are provided with cooperating catch and abutment means which are released one from the other by rotating the needle 90.degree. relative to the tubing (or vice versa). The tubing is manufactured from spring-tempered carbon steel or chrome nickel steel and is secured to the suture by heating the tubing and then swaging to the suture.
U.S. Pat. No. 3,311,100 relates to a flexible composite suture having a tandem linkage. The needle is secured to a flexible suture leader manufactured from a readily sterilizable plastic such as nylon, linear polyethylene, isotactic polypropylene, polyester, silk or other proteinaceous material, e.g. by inserting and crimping the leader within an axial bore in the needle shank. The opposite end of the suture leader is crimped within a connector sleeve of a thin walled metal tubing, e.g., stainless steel. The opposite end of the tubing is crimped around a stiff suture, e.g., monofilament stainless steel.
U.S. Pat. No. 3,918,455 describes a needle-suture attachment wherein a hollow suture portion is secured to the shank end of a needle which is of reduced cross-section as compared to the remainder of the needle.
Additional patents which describe the use of tubing to effect suture-needle attachment include U.S. Pat. Nos. 4,672,734 (forming needle from U-shaped metal plate around suture), 4,359,053 (silicone tubing), 3,835,912 (laser welding of metal tube to needle), 2,814,296, 2,802,468 (chamfered tubing ends), 2,302,986, 2,240,330, 1,981,651 (needle and tubing screw threaded), 1,960,117 and 1,591,021.
Numerous disadvantages exist with methods used heretofore to effect needle-suture attachment. For example, those methods which involve the formation and use of an axial bore in the shank end of the needle require the use of expensive hole forming equipment. Moreover, it is difficult to maintain the bore concentric with the center-line of the needle and to control the depth (and diameter) of the bore when drilling the needle shank, whether using conventional drilling equipment or laser drilling. Another disadvantage is the possibility that foreign substances may inadvertently or uncontrollably be introduced into the needle bore, e.g., oil used during drilling or silicone from the needle silconization process. Safeguards employed in an attempt to prevent the introduction of such foreign materials, e.g., water blocking during needle silconization, are inconvenient, adding time, effort and cost to the needle production process.
Attachment processes which employ bored needle shanks also limit the range of materials from which needles may be fabricated in a cost effective fashion. For example, it is exceedingly difficult to drill Series 300 stainless steel (laser drilling is required) and, once drilled, it is difficult to swage Series 300 stainless steel in a consistent and reliable manner. For this reason, Series 300 stainless steel is not employed for the vast majority of needled suture products despite its advantageous combination of strength and ductility characteristics as compared to conventionally employed Series 400 stainless steel.
Additional disadvantages associated with needle-suture attachment methods which employ bored needle shanks include the weakness imparted to the bored section of the needle, particularly after swaging, and the attendant increased possibility that the needle will fracture in this region. It is also difficult to provide a specialized surface finish to the needle shank to assist in needle attachment, e.g., a texturized surface and/or a tapered bore. Swaging equipment used in such needle-suture attachment methods is also maintenance intensive.
Needle-suture attachment methods which have employed tubings heretofore also exhibit numerous disadvantages. Methods which employ metal tubings greatly diminish the flexibility of the needle-suture combination in the attachment region. Such diminished flexibility has a deleterious effect in many surgical procedures. Swaging of the tubing to the needle and the suture is also undesirable in that swaging is time-consuming, maintenance intensive, and subject to variability in attachment force.
Moreover, needle-suture attachment methods which have employed tubings heretofore have necessarily required the use of tubing having an inner diameter essentially equal to the outer diameters of the needle shank and suture tip to be attached. Too large a difference between the aforesaid inner and outer diameters inhibits the attachment process, and prevents a tight, secure interface between needle (and/or suture) and tubing. The limited tolerance between the tubing inner diameter and the needle shank/suture outer diameters in such methods make these dimensions critical, thereby making the attachment process more difficult and time-consuming, and increasing the likelihood of attachment failure and/or rejected materials.
With regard to conventional detachable needles, a further disadvantage is that such needles heretofore have been attached by swaging or crimping. It is difficult to sufficiently control the swaging process in day to day manufacture so as to consistently obtain suture-needle devices which consistently detach under the same force with minimal variation in detachment force. Indeed, conventional swaged detachable needles have been observed to fail prematurely under minimal force, e.g. in removing the suture from the package, or to fail to yield under considerable force. Such events can result in unnecessary waste, lost time and, at worst, unavailability of a suture-needle to the surgeon when needed.
Commonly assigned, copending U.S. patent application Ser. No. 413,240, filed Sep. 27, 1989, describes a combined surgical needle-suture device and surgical needle-suture attachment method which overcomes the aforementioned drawbacks of the previously known needle-suture combinations and needle-suture attachment methods. In accordance with said application, a combined needle-suture device is provided in which a surgical needle having a shank of reduced cross-section is attached to a suture through a shrinkable tubing, or micro-ferrule, which is fitted about the needle shank and a portion of the suture. Application of energy to the shrinkable tubing brings the tubing into engagement with both the needle shank and the suture. The physical and chemical characteristics of the shrinkable tubing material, the relative diameters of the tubing, the needle shank and the suture, and the amount of energy applied to the tubing may be controlled to provide a needle-suture combination having a desired pull-out force. It is thus possible to produce standard needle-suture combinations and removable needle-suture combinations using a single attachment process and a common inventory of materials.